Welding Tips and Tricks

I didnt know where to post this, so, its here.
Its an image of a microscopic crack in steel, taken with an ''Electron Microscope''.
I found it on a russian web site. I thought it was interesting.

Do you know, is this carbon steel?

Any other images like aluminum? For some reason aluminum seems to pull apart more to my eye, was just curious.

Page didnt specify type of steel. Only one pic like this, was a real conglomeration of pics, oddities.

Amazing photo, thanks for sharing, along with the source...